UC Irvine

The ATLAS measurement of the inclusive top quark pair (tt¯$$t\bar{t}$$) cross-section σtt¯$$\sigma _{t\bar{t}}$$ in proton–proton collisions at s=8$$\sqrt{s}=8$$ TeV$$\,\mathrm{TeV}$$ has been updated using the final 2012 luminosity calibration. The updated cross-section result is: σtt¯=242.9±1.7±5.5±5.1±4.2pb,$$\begin{aligned} \sigma _{t\bar{t}}= 242.9\pm 1.7\pm 5.5\pm 5.1\pm 4.2\,\mathrm pb, \end{aligned}$$where the four uncertainties arise from data statistics, experimental and theoretical systematic effects, knowledge of the integrated luminosity and of the LHC beam energy. The result is consistent with theoretical QCD calculations at next-to-next-to-leading order. The measurement of the ratio of tt¯$$t\bar{t}$$ cross-sections at s=8$$\sqrt{s}=8$$ TeV$$\,\mathrm{TeV}$$ and s=7$$\sqrt{s}=7$$ TeV$$\,\mathrm{TeV}$$, and the s=8$$\sqrt{s}=8$$ TeV$$\,\mathrm{TeV}$$ fiducial measurement corresponding to the experimental acceptance of the leptons, have also been updated.